Anticopying film

ABSTRACT

An anticopying film or layer consists of a film or of a layer of transparent material having a large number of completely or partially nontransparent regions which are arranged distances apart and whose planes are arranged in about the same predetermined position relative to the surfaces of the film or of the layer so that, from a predetermined viewing angle onto the surfaces of the anticopying film, the latter is essentially transparent. The regions consist at least partially of photosensitive material which is converted by the action of radiation into nontransparent or reflecting material, it also being possible to provide, in the transparent plastics material, furrows or grooves in which the photosensitive material is present.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to an anticopying film or layer,consisting of a film or of a layer of transparent material having alarge number of partially or completely nontransparent regions which arearranged distances apart and whose planes are arranged in about the samepredetermined position relative to the surfaces of the film or of thelayer so that, from a predetermined viewing angle onto the surfaces ofthe anticopying film, the latter is essentially transparent.

2. Description of the Related Art

An anticopying film of the type defined as above is described in U.S.Pat. No. 3,887,742. Such a film, which is intended to permit copy-proofdocuments, is effective in concealing graphic information and/orcharacters of a document or a text generally, in the vertical viewingdirection as occurs in a copier, and in rendering visible the graphicinformation and/or characters at a predetermined different viewingangle, relative to the plane of the document.

In practice, such an anticopying film is a transparent plastics filmcontaining nontransparent particles or having a surface which is notchedin any manner or has a sawtooth-shaped cross-section, wherein a firstoblique or vertical surface is either black or reflecting from avertical viewing angle, relative to the plane of the film or of thedocument, and the other oblique surface is transparent at a differentviewing angle, so that the information or characters are legible. Suchnotched or sawtooth-shaped surfaces are very difficult to produce sincethe surfaces must first be embossed or beaten and the oblique surfacesmust then be provided with a black or reflecting material, it beingnecessary for the accuracy of these operations to be so high that thetransparent surfaces do not suffer, ie. are likewise provided partiallywith black and reflecting material. In a further embodiment, black inkwhich covers at least a part of the background is provided in the valleybetween two successive teeth in a film surface having a sawtooth-shapedcross-section. Here too, no practical production processes have beendescribed.

An anticopying medium for written or printed matter is disclosed inAU-A-610 614, wherein the medium contains a photosensitive ink systemwhich, when exposed in a photocopier, renders the text illegible ormakes the copy clearly distinguishable from the original, so that eitherthe original becomes worthless or is clearly recognizable as having beencopied.

SUMMARY OF INVENTION

It is an object of the present invention to provide an anticopying filmor an anticopying layer, which film or which layer is simpler to produceand more economical and prevents or at least complicates copying.

We have found that this object is achieved by an anticopying film orlayer for documents, consisting of a film or of a layer of transparentmaterial having a large number of partially or completely nontransparentregions which are arranged distances apart and whose planes are arrangedin about the same predetermined position relative to the surfaces of thefilm or of the layer so that, from a predetermined viewing angle ontothe surfaces of the film or of the layer, the anticopying film isessentially transparent, wherein the regions consist partially orcompletely of a material which is photochemically converted intonontransparent or reflecting material.

This considerably simplifies the production of such a film or layer, andthere are advantageous possibilities for variation, depending on theparticular desired use.

We have found that the object is furthermore achieved in practice by ananticopying film or layer, consisting of a film or of a layer oftransparent material having a large number of partially or completelynontransparent regions which are arranged distances apart and whoseplanes are arranged in about the same predetermined position relative tothe surfaces of the film or of the layer so that, from a predeterminedviewing angle onto the surfaces of the film or of the layer, theanticopying film is essentially transparent, if the regions are producedfrom coextruded transparent and nontransparent plastics material.

The anticopying film or the anticopying layer is thus produced in oneoperation.

We have found that the object is furthermore advantageously achieved byan anticopying film or layer consisting of a film or of a layer oftransparent material having a large number of partially or completelynontransparent regions which are arranged distances apart and whoseplanes are arranged in about the same predetermined position relative tothe surfaces of the film or of the layer so that, from a predeterminedviewing angle onto the surfaces of the anticopying film, the latter isessentially transparent, if the regions consist of nontransparent orreflecting strip material which, after extrusion of the transparentmaterial with furrows or grooves, is inserted into said furrows orgrooves.

This provides a further advantageous embodiment of such an anticopyingfilm.

In an advantageous embodiment, the nontransparent regions are obliquelayers which consist of exposed and, if necessary, developedphotosensitive material.

The transparent material consists, for example, of a thick photoemulsion which is partially exposed and then developed.

In this case, the oblique layers are essentially present continuouslythrough the thickness of the film or of the layer.

The transparent material may also consist of a plastic which contains atleast one photosensitive substance, and the exposure can be localizedand effected in a plane which is oblique relative to the materialsurface. Developing is not necessary even in this case.

In a further embodiment, the film or the layer may be provided, in atleast one surface, with a large number of roughly parallel and roughlyequidistant furrows or grooves, into which the one or morephotosensitive substances are introduced.

The furrows or grooves may be arranged at right angles or obliquely tothe film or layer surface.

It may also be advantageous in practice if the nontransparent orreflecting regions are formed as first opaque or reflecting layers onthe upper surface of the film or of the layer and as second opaquelayers, arranged horizontally staggered with respect to the first opaquelayers, on the lower surface of the film or of the layer.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention are described below with reference toschematic drawings:

FIG. 1A shows an anticopying film having opaque oblique layers

FIG. 1B shows an anticopying film having a sawtooth cross-section at thesurface

FIG. 2A shows an anticopying film having rectangular grooves andunexposed photosensitive material therein

FIG. 2B shows an anticopying film having diamond-shaped groovesaccording to FIG. 2A

FIG. 3A shows the rectangular grooves from FIG. 2A with exposed, opaquephotosensitive material

FIG. 3B is a variation of FIG. 3A, wherein the oblique layers SS are setat an angle γ in the manner of FIG. 2B.

FIG. 4A shows a double-sided groove embodiment according to FIG. 3A

FIG. 4B shows a double-sided groove embodiment according to FIG. 3B.

DETAILED DESCRIPTION

For the purposes of the present invention, photochemically convertiblematerial is any photosensitive material which changes in its physicalproperties as a result of the action of radiation (photons, corpuscles),in this case from a transparent to an opaque state.

FIG. 1A shows an anticopying film F or an anticopying layer consistingof transparent plastics material in which a number of parallel equallyspaced oblique layers SS are provided, the layers SS being presentcontinuously through the total thickness d of the anticopying film F.

The plastics material preferably contains photosensitive substanceswhich are reactive in incident light of a specific wavelength and renderthe affected regions opaque.

The action of light can be localized by means of masks to thepredetermined regions of the oblique layers, or arrays or a matrix canensure limited incident light. Such arrays may be photodiode ordiffraction grating arrangements which make it possible to produce alarge number of light sources. However, it is also possible to use alocally controlled laser beam or a plurality thereof. The radiationshould be obliquely incident in order to be able to form the obliquelayers SS at the predetermined angle γ of from about 30° to about 73°,in particular from about 45° to about 60°. At the angle γ or in thedirection of view indicated by the arrow VI, the information I of thedocument D is visible through the transparent layers TS. In thedirection of arrows VV, however, the information I is concealed andinvisible.

The opacity of the layers SS must therefore be chosen so that theinformation in any case is at least unclearly recordable by commercialcopiers and cannot be read from the copy by people.

FIG. 1B shows an anticopying film F1 or an anticopying layer having asurface OS which possesses a sawtooth-shaped cross-section. One sidewallof the sawtooth shape is arranged, for example, at an angle γ and theother is roughly vertical. The triangular furrows E are in turn filledwith plastic PH containing photosensitive material, for example everysecond furrow E2 being opaque (PHE) and every first furrow E1 remainingroughly transparent as a result of localized incident light, asdescribed above. The oblique surfaces Q may be optically formed suchthat the total reflection occurs in the case of radiation at rightangles, or they may be formed with a reflecting layer QS. This likewiseresults in an oblique viewing direction corresponding to the directionVI and a roughly vertical concealment direction VV (FIG. 1).

The film or layer material F1 should be transparent plastics materialwhich is formed either as self-supporting film or as a layer of thistype (F1) or is provided with a substrate film or substrate layer G.

The furrows in the surface OS may be embossed or may be formed in theproduction, for example by extrusion, or mechanically, for example bycutting.

FIG. 2A shows a further anticopying film F3 or anticopying layerembodiment having longitudinal grooves NU which are roughly rectangularin cross-section and in turn are filled with photosensitive material PHas described above for FIG. 1B. The plastic of the base material is onceagain transparent and the grooves NU are introduced by the methodsdescribed. The material PH is uniformly exposed (arrow LU) and becomesopaque (PHE), as indicated by the shading in FIG. 3A. In thisarrangement of the grooves NU, only partial information PI can be copiedby exposure at right angles VV in the copier, while the additionalinformation PP is visible only at an angle (in this case about 63°).

Thus, only partial concealment is achievable here.

Another embodiment of an anticopying film F3 or anticopying layer, whichembodiment is more advantageous in this respect, is shown in FIG. 2B.

The diamond-shaped grooves RU here are either produced as grooves NU(FIG. 2A) and then subjected to a shear stress in the direction SR orare produced in this form by extrusion, cutting, etc. The photosensitivematerial filling PH is the same and is introduced, for example, by knifecoating. After uniform exposure by means of radiation source LU, thefinished anticopying film F3 or anticopying layer having opaque obliquelayers SS in the angular range γ (see above) is obtained, as shown inFIG. 3A. In the Examples of FIGS. 2 and 3, the grooves NU and RU,respectively, are present through up to about half the thickness d ofthe film F2 and F3, respectively. They may also be deeper. The depth Tof the grooves NU and RU can be formed to correspond roughly to thetotal thickness d only if a substrate film or substrate layer G, notshown here, is used, to which the layer F2 or F3 is fastened or applied.

FIG. 4A shows a film F4 or layer provided with rectangular grooves NU onboth sides in comparison with F2. The grooves NU1 in the upper surfaceand NU2 in the lower surface are arranged staggered relative to oneanother. The opaque groove content is produced, as described above, bymeans of a photochemical material PH and uniform exposure thereof (PHE).

In the direction VV, the information I is once again completelyconcealed.

In the directions VI and VII, partial information is visible in eachcase, the completeness of the visible information increasing with adecrease in the depth T of the grooves NU1 and NU2, independently of thewidth bb of the individual grooves NU1 and NU2.

FIG. 4B shows a film or layer embodiment F5 which corresponds to FIG. 4Aand, in contrast to F3, is formed on both sides with oblique layers SS1and SS2, which can be produced as described above. The oblique layersSS1 and SS2 are arranged horizontally staggered relative to one another.

The information I is concealed in the vertical viewing direction VV andat least partially visible in the oblique direction VI.

The groove or furrow embodiments in FIGS. 1B, 2A and B, 3A and B and 4Aand B can also be realized with opaque or reflecting, strip-like inlaysK instead of photosensitive grooves or furrow contents.

Said inlays can be inserted into the furrows or grooves, for exampledirectly after extrusion of the furrowed or grooved material.

It is even simpler directly to form the opaque or reflecting strip-likefurrow or groove contents by coextruding a transparent plastic and anopaque plastic OK (FIG. 1).

An anticopying film or layer consists of a film or of a layer oftransparent material having a large number of completely or partiallynontransparent regions which are arranged distances apart and whoseplanes are arranged in about the same predetermined position relative tothe surfaces of the film or of the layer so that, from a predeterminedviewing angle onto the surfaces of the anticopying film, the latter isessentially transparent.

The regions consist at least partially of photosensitive material whichis converted by the action of radiation into nontransparent orreflecting material, it also being possible to provide, in thetransparent plastics material, furrows or grooves in which thephotosensitive material is present.

We claim:
 1. An anticopying film, consisting of a film of transparentmaterial having a large number of nontransparent or reflecting layerswhich are arranged essentially equal distances apart and whose planesare arranged essentially parallel to one another and in about the samepredetermined position relative to the surfaces of the film on at leastone of the surfaces, wherein from a predetermined oblique viewingthrough angle from about 30° to about 73° onto the surfaces of theanticopying film, the latter is essentially transparent and, and whereinthe nontransparent or reflecting layers are formed at least partiallyfrom exposed photosensitive material and the nontransparent orreflecting layers are located on the upper and lower surfaces of theanticopying film and are arranged obliquely relative to the surface ofanticopying film as to provide for said predetermined oblique viewingangle.
 2. An anticopying film as claimed in claim 1, wherein thenontransparent or reflecting layers are formed as oblique layerscontinuously through the thickness of the film.
 3. An anticopying filmas claimed in claim 1, wherein the nontransparent or reflecting layersare formed as first opaque or reflecting layers on the upper surface ofthe film and as second opaque or reflecting layers, arrangedhorizontally staggered with respect to the first opaque or reflectinglayers, on the lower surface of the film as to provide for saidpredetermined viewing angle.
 4. An anticopying film as claimed in claim1, wherein the film is provided, on at least one surface, with a largenumber of essentially parallel, essentially equidistant furrows orgrooves in which at least one exposed photosensitive substance (PH) ispresent.
 5. An anticopying film as claimed in claim 4, wherein thefurrows or grooves are provided at right angles to the film surface. 6.An anticopying film as claimed in claim 4, wherein the furrows orgrooves are arranged obliquely to the film surface.
 7. An anticopyingfilm as claimed in claim 4, wherein the furrows or grooves have atriangular shape.
 8. An anticopying film as claimed in claim 1, whereinthe transparent material contains at least one photosensitive substance.9. An anticopying film, consisting of a film of transparent materialhaving a large number of nontransparent or reflecting layers which arearranged essentially equal distances apart and whose planes are arrangedessentially parallel to one another and in about the same predeterminedposition relative to the surfaces of the film on at least one of thesurfaces, wherein from a predetermined oblique viewing angle throughonto the surfaces of the anticopying film, the latter is essentiallytransparent and wherein the film consists of coextruded, transparentplastic and nontransparent or reflecting plastic material, the latterbeing formed from exposed photosensitive material and form thenontransparent or reflecting layers, which are located on the upper andlower surfaces of the film and are arranged obliquely relative to thesurfaces of the anticopying film as to provide for said predeterminedviewing through angle.
 10. An anticopying film, consisting of a film oftransparent material having a large number of nontransparent orreflecting layers which are arranged essentially equal distances apartand whose planes are arranged essentially parallel to one another and inabout the same predetermined position relative to the surfaces of thefilm on at least one of the surfaces, wherein from a predeterminedviewing angle through from about 30° to about 73° into the surfaces ofthe anticopying film, the latter is essentially transparent, and whereinthe nontransparent or reflecting layers consist of nontransparent orreflecting strip material which is inserted into furrows or grooves of acoextruded transparent material, the nontransparent or reflecting layersbeing located on the upper and lower surfaces of the film being arrangedobliquely relative to the surface of the film as to provide for saidpredetermined oblique viewing through angle.
 11. An anticopying film asclaimed in claim 10, wherein first nontransparent or reflecting layersof strip material are located on the upper surface of the film sandsecond nontransparent or reflecting layers of strip material are locatedon the lower surface of the film and said first and secondnontransparent reflecting layers are arranged horizontally staggered toone another as to provide for said predetermined viewing through angle.12. An anticopying film as claimed in claim 1 wherein the predeterminedviewing through angle is from about 45° to about 60°.
 13. An anticopyingfilm as claimed in claim 9 wherein the predetermined viewing throughangle is from about 45° to about 60°.
 14. An anticopying film as claimedin claim 10 wherein the predetermined viewing through angle is fromabout 45° to about 60°.